I believe the answer is: British expeditionary force
British expeditionary force was a group of soldiers that created in world war 2 in order to help the fight against nazi in the western front.
At that time, The French surrendered to the nazi only within 30 days the nazi's initial attack and the British expeditionary force was sent there to help its ally. But the nazi's forces got the better of them in the combat and they're forced to escape from Dunkirk.
